PORT ST. LUCIE, Fla. -- It hasn’t been a pleasant week for John Maine, who had a migraine headache Tuesday and a stomach bug during his start Thursday. Maine said he threw up before the game and in the clubhouse between innings.

Considering the shoulder injuries he has had the last two seasons, though, Maine didn’t mind feeling under the weather in his final spring start.

Maine allowed four runs on six hits and four in 4 2/3 innings. He held the Nationals scoreless through the first three innings, but with his stomach bothering him he wore down quickly after that.

Maine finished with a 7.88 Grapefruit League ERA, but said he is throwing the ball better than he has in two years.

“I think the last time it came out easy without trying to really force anything was spring training 2008,” Maine said. “I might have been throwing a little harder then, but it’s coming out good.”

Maine will make his first regular-season start Tuesday against the Marlins at Citi Field.

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The Mets’ clubhouse cleared out after Thursday’s game as players boarded a bus to St. Petersburg, but Carlos Beltran wasn’t going anywhere. The center fielder is still rehabbing from offseason knee surgery and will remain here for the foreseeable future.

Beltran said he is primarily doing balance and strength exercises now, while playing catch and tracking balls in an indoor batting cage. He said he expects to start running around April 10 but was reluctant to put a timetable on anything else.

“I don’t want to talk about when I can come back because I don’t know yet,” Beltran said. “When I run, then that can give me an idea of where I am. Right now it’s hard for me to say because I haven’t run.”

The expectation remains that Beltran will return sometime around mid-May.

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Manager Jerry Manuel said the team will need someone in addition to Alex Cora who can play shortstop until Jose Reyes returns, even if Reyes is only on the disabled list for the first week of the season. With Cora starting, look for either Ruben Tejada or Russ Adams to make the Opening Day roster as a reserve.